Cell aggregate plan is found in

Options

A. Cnidarians
B. Sponges
C. Roundworms
D. Flatworms

Answer

To solve the question "Cell aggregate plan is found in:", we will analyze the options provided: cnidarians, sponges, roundworms, and flatworms.

### Step-by-Step Solution:

1. **Understanding Cell Aggregate Plan**: The term "cell aggregate plan" refers to a body organization where cells are grouped together but do not form true tissues or organs. This is a key characteristic of certain organisms.

2. **Identifying the Organism Groups**:
- **Cnidarians**: These organisms, such as jellyfish and corals, exhibit a tissue level of organization. Their cells are organized into tissues, which means they do not fit the definition of a cell aggregate plan.
- **Sponges (Phylum Porifera)**: Sponges have a cellular level of organization. Their cells are loosely organized and do not form true tissues or organs, which aligns with the definition of a cell aggregate plan.
- **Roundworms**: These organisms have a more complex body organization, classified as organ system level. They possess organs and systems, thus not fitting the cell aggregate plan.
- **Flatworms**: Similar to roundworms, flatworms also have an organ and organ system level of organization, which means they do not fit the cell aggregate plan either.

3. **Conclusion**: Based on the analysis, the only group that exhibits a cell aggregate plan is sponges, which belong to the phylum Porifera. Therefore, the correct answer is **sponges**.

### Final Answer:
The cell aggregate plan is found in **sponges** (Phylum Porifera).

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